JP-A 3-22619 discloses a positive photoresist composition comprising an alkali-soluble resin and an alkali-insoluble 1,2-quinonediazide compound. When this composition is exposed to UV through a mask and developed with a developer in the form of an aqueous alkaline solution, the composition can form a resist pattern faithful to the mask pattern at a high resolution because the composition is scarcely dissolvable or swollen in an aqueous alkaline solution as the developer. Spedifically, the 1,2-quinonediazide compound in the exposed areas is converted to alkali-soluble indene carboxylic acid while the unexposed areas to form the resist pattern are little changed during development. In the current industry requiring higher integration of ICs, positive photoresists featuring resolution are used most often.
In the field of manufacturing liquid crystal display devices using small-size glass substrates, the resist applying method used is a spin coating method of dropping a resist solution at the center of a substrate and rotating the substrate. The spin coating method ensures coating uniformity. In the case of large-size substrates of the 1×1 meter square order, however, considerably large amounts of resist solution are spun off during rotation and thus discarded. The high-speed rotation also causes substrates to be broken and raises a problem in taking a cycle time. Since the coating ability of a spin coating method involving central dropping and rotation depends on the rotational speed and the coating weight of resist solution, a problem arises if the spin coating method is applied to more large-sized substrates of the fifth generation (of approximately 1,000 mm×1,200 mm to 1,280 mm×1,400 mm). That is, there are available no general-purpose motors capable of acceleration as needed. Customizing a special motor leads to increased part costs. Because the performance parameters required for the coating process including a coating uniformity of ±3% and a cycle time of 60-70 sec per substrate remain unchanged even when the substrate and the apparatus become enlarged in size, the spin coating method involving central dropping and rotation is difficult to accommodate the requirements other than coating uniformity.
Under the circumstances, a resist coating method of nozzle injection is proposed as a new resist coating method that can comply with large-size substrates of the fifth or later generation.
Meanwhile, surfactants are added to positive photoresists for the purposes of improving coating efficiency and striation as well as the developability of radiation-exposed areas after dry film formation. Among others, fluorochemical surfactants and fluorine-silicon surfactants are widely utilized for leveling and coating characteristics.
JP-A 2000-181055 discloses a positive photoresist composition suitable for liquid crystal device manufacture comprising a non-ionic fluorine-silicon surfactant having specific fluorine and silicon contents, which can be effectively coated without striation, drying unevenness and dripping marks, and are good in resist pattern profile as essentially required for compositions of this type. However, this photoresist composition is still unsatisfactory in that streaks can form on a coating if the composition is applied by the nozzle injection coating method referred to above.
While continuous demands for larger size and higher definition are imposed on substrates, it would be desirable to have a positive photoresist composition which ensures coating uniformity even when coated over large areas and are improved in resist pattern profile as essentially required for compositions of this type.